Stabilized coloring compositions and methods of making and using same



2,755,200 Patented July 17,1956

STABILIZED COLORING COMPOSITIONS AND METHODS OF MAKING AND USING SAME Walter Jean Balon, Carneys Point, and Otto- Stallmann,

Brltlgeton, N. J., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application December 28, 1953, Serial No. 400,776

28 Claims. (Cl. 117-36) This invention relates to new coloring compositions of matter. More particularly this invention deals with novel compositions of matter which are in a storagestable, colorless form per se, but which are adapted to generate coloring matters of the. triarylmethane series upon being treated with acid reacting alcoholic or aqueous solutions, or upon being brought into forceful contact with acid reacting compounds.

It is an object of this invention to provide improved coloring compositions for use in duplication processes such as spirit hectograph printing, impact printing, or ordinary typing when carbon copies are made. A further object is to provide coloring matters of the aforementioned type adapted for coating carriers, such as the so-called carbon paper" or the master sheets for hecto- 1 achievements of this invention will appear as the descrip- 1 tion proceeds.

By spirit hectograph printing, in this specification, we mean multi-copy duplication from a master sheet which carries a heavy imprint of a reverse image of the desired writing. Copies are made from this master sheet by bringing copy sheets successively into contact with the imprinted face of the master sheet, usually in some form of a rotary-cylinder machine. In impact printing, the duplicating coating is colorless but develops color locally through the pressure of a stylus or the impact of a typewriter key. In this type of printing, the coating is often on the copy sheet itself; or it may be on a separate sheet from which it is transferred to the copy sheet by the same pressure or impact. In such cases the coating generally comprises sveral superimposed films, of which one carries the coloring agent, one contains the developer, and an intermediate waxy film serves to separate the two; in use, the impact of the typewriter key ruptures the insulating film locally and brings the color and developer into intimate contact with each other at those points. Again, the coating may consist of two cooperating parts, of which one is on the copy sheet and one is carried on a transfer sheet, which is analogous to ordinary carbon paper" except that the coating is colorless. As in the case of ordinary typing with carbon paper, impact printing produces one copy per coating. The two processes will therefore be referred to hereinafter as single-copy processes, although of course several sheets and coatings may be stacked up behind each other so as to produce several copies by a single impression or typing.

In the carriers for producing master sheets, for instance hectograph carbons and typewriter ribbons, as well as in the transfer sheets for ordinary typing .with production of carbon copies, the colors of the triarylmethane series have come to be recognized as the standthese liquids.

merce in the form of chlorides.

ard coloring matters. The reason for this lies firstly in the intensity of their color, and secondly in their ready solubility in water and alcohols, which facilitates their transfer from the master to a copy sheet moistened with A particularly popular group, of colors within the mentioned broad family is the group of N-polyalkyl-tri(p aminophenyl) methanes which generally occur in com- Methyl violet, crystal violet and ethyl violet are common commercial members of this group, but it may embrace also other. poly lower-alkyl derivatives such as propyl, isopropyl,n-butyl, isobutyl, or mixed alkyl radicals, the word poly being here used to indicate the presence of not less than 5 and not more than,6 such lower alkyl radicals per molecule. This particular subgroup of colors has gained a strong foothold in the mentioned art, because of its reasonable price, and outstandingly high tinctorial strength, being capable of yielding as many as 500 readable hectograph copies from one master sheet. I t

On the other hand, the mentioned group of colors have the great draw-back of coming easily off the coating onto the hands of the typist or the operator of the duplicating machine, and of producing tenaciously adhering stains upon their skin or clothes. Such stains do not wash off readily with soap and water.

This invention contemplates solving the above problem by producing the mentioned coloring substances in an intermediate, colorless form, which however will develop the desired intensely violet color upon being transferred to the copy. More particularly, this invention contemplates coating the transfer medium (carbon paper" or typewriter ribbon) with a colorless form of the carbinols of the respective colors, producing white carbon paper or white typewriter ribbon.v These colorless transfer media are contemplated for use in the ordinary manner, except that provision is to be made for developing the colorless imprint into a colored image by the action of acid. In the case of hectograph duplication, this can be achieved by adding an acid or an acid-developing halogen compound to the moistening medium (alcoholic composition, acetone or other polar solvent), employed in producing'the copies. In thecase of impact printing, an acid clay may be incorporated in the transfer coating (properly insulated by a waxy film from the colorless coating containing the coloring agent, until the instant of impact), or in the paper used for the copy. Asa matter of fact, many papers naturally contain aluminum silicates or similar acid clays as a result of their process of manufacture, and are thus adapted directly for developing the imprint produced upon them with the novel colorless carbon papers of this invention.

To illustrate more clearly, what we mean, we give here the formulas for crystal violet and its carbinol, these being typical of the entire group.

i o 4 aMal Crystal violet (salt form) HO ClCsHsN CH3) 21s Oarblnol 6: crystal violet The colored substance is the salt form. The carbinol is merely an earlier stage in the manufacture of this color, and is readily converted into the color by treatment with acid.

When isolated in pure form, in small quantities on a laboratory scale, the carbinol is colorless. This state, however, is unstable and quickly becomes converted into color, presumably by absorbing CO: from the atmosphere.

Whatever the explanation be, it is a fact that commercial carbinols as obtained in the plant are highly colored. Consequently, the use of carbinols as hitherto manufactured cannot solve the aforementioned problem of stain- Now we have found that carbinols of lower N-polyalkyl-tri-(p-aminophenyl) methanes may be decolorized and stabilized against rapid discoloration on exposure to the atmosphere by interacting the same with certain organic bases as more fully set forth hereinbelow under the condition indicated hereinbelow. Furthermore, this stable composition nevertheless yields readily to acids, for instance hydrochloric, sulfuric, nitric or oxalic, to certain acid-developing halogen compounds as more fully defined below, and also to acid clays of the types used in impact printing. As a consequence, the novel carbinol compositions of the mentioned colors are ideally adapted for the purposes hereinabove discussed, that is, production of non-staining coatings on transfer media for duplication processes.

The novel treatment hereinabove indicated comprises, in its simplest form crystallization of the carbinol from an alcohol with which it will not react to form an ether, in other words, a secondary or tertiary alcohol, in the presence of a quaternary nitrogenous base which contains alkyl, aralkyl, cycloalkyl, hydroxyalkyl or epihydrin groups. Common examples of such quaternary nitrogenous bases are: henzyl-trimethyl-ammonium hydroxide, tetramethyl-ammonium hydroxide, phenyl-dimethyl-benzyl-ammonium hydroxide, and N-methyl-pyridinium hydroxide. Other quaternary nitrogenous bases possessing shortchain aliphatic groups are also suitable, for instance the reaction product of epichlorhydrin and ammonia produced according to U. S. P. 1,977,251. Although the patent formulates the product as a secondary amine, more recent researches have revealed that the product is essentially a quaternary base.

In general any colorless quaternary ammonium hydroxide is suitable for our invention. Thus, the substituents on the N-atom may be alkyl, hydroxyalkyl, epihydrin, cycloalkyl, aralkyl or aryl radicals, or the N- atom may be part of a heterocyclic ring. The only additional restriction upon the ammonium base is that it be soluble to a workable degree in the alcohol selected as solvent. For this reason, the ammonium base should be free of sulfo and carboxy groups.

The function of the quaternary ammonium base is not clearly understood. No doubt the quaternary compound will complete the alkylation of the third N-atom in methyl violet whenever this is used by itself or as an intentional or incidental admixture to crystal violet. But analysis shows that the carbinols of this invention have higher nitrogen contents than correspond theoretically to the structures of the fully hexaalkylated carbinols. It follows that the quaternary ammonium hydroxide interacts in some manner with the fully methylated carbinol. We have not found, however, any evidence that a mere chemical reaction takes place, inasmuch as the excess nitrogen content of the product over theory is not constant, but varies with the quantity of the quaternary base added. it is possible that we deal here simply with a case of occulsion of the base by the carbinol in the process of crystalliution. The minimum quantity of occluded stabilizing agent observed by us to be reasonably effective for the purposes of this invention is about l equivalent weights of the base per 100 moles of the carbinol. There appears to be no upper limit. except the economical consideration of diluting the coloring substance too much by non-coloring material. Furthermore. the more the quantity of ammonium base added, the higher will be the required amount of acid furnished by the agent employed for developing the color during transfer. As a practical rule, therefore, the quantity of added quaternary base will generally be from about 2.5 to by weight of the 4 carbinol being protected, but may be as high as 20% or more if desired.

The alcohol, as already indicated, should be one which does not form an ether with the carbinol. Primary alcohols are known to do this. Therefore, we prefer to exclude alcohols having primary alcoholic am F. that is the group --CHsOH. This leaves for consideration secondary and tertiary alcohols. Among these we have found noexceptions as to usefulness, so long as the alcohol is one which is liquid or melts at a convenient temperature, say below C., and so long as it exerts suflicient solvent action upon the carbinol, to permit the use of reasonably small volumes of liquid. Convenient therefore are secondary and tertiary, aliphatic, monohydric, saturated alcohols of 3 to 6 carbon atoms, for instance isopropyl, sec. butyl, tert, butyl, sec. amyl, tert. amyl and cyclohexyl.

The quantity of the alcohol employed is not critical. It should be sutlicient to dissolve the quantity of carbinol being treated, or at least the major portion of it, at the temperattne selected, without unduly increasing the volume of the required apparatus. The required volume of total solvent may also be decreased considerably by adding to the secondary or tertiary alcohol a non-polar solvent such as benzene, toluene or xylene. The quantity of added non-polar solvent may be as high as 1:] by volume with reference to the alcohol. In this fashion the total amount of solvent required for a given quantity of carbinol may be reduced by 50% or more.

The temperature selected for the treatment is governed by practical considerations, it being understood that solution more rapid as the temperature goes up. Convenient practical temperatures are, say, 60' C. to the boiling point of the alcohol or solvent mixture chosen. The latter will usually be about 80' C.-l00' C., but may be as high as C.

For the carbinol, a commercial grade of the same may be chosen. As already noted, this is always deeply colored due to contact with acids in handling or on exposure to the atmosphere. Alternatively, one may start with the chloride or other convenient commercial salt-form of the color. In both cases, the quantity of quaternary base added should be sufficient to basify the salt fraction of the color and to provide a concentration of the ammonium base of at least 5% by weight of the color, during the crystallization of the mass.

Alternatively, the chloride fraction of the color may be basifiedbysodiumorpotassitnnhydroxide,andthena quanutyofquaternaryammonimnbaaeequaltoaboutS to 20% by weight of the carbinol may be added. It will benotedherethatinasmuchassomeofthequaternary base will necessarily remain in the alcoholic mother liquor, the quantity thereof to be added (in excess ofany quantity required for basitication of the chloride) will generally be about twice the percentage sought to be entered into the crystals of the product.

Heating at the selected temperature is continued until all color has disappeared. If the quantity of alcohol and temperature of heating are optimum for the chosen alcohol, this clarification will appear suddenly. Subsequent cooling will precipitate the desired colorless, color-stable crystals.

As far as we have learned hitherto, the primary stabilising eflect is limited to quaternary ammonium compounds asabovedeflned. Otherbases,forinstancepotamium carbonate or sodium hydroxide do not achieve this elect. But we have found that this primary effect can be increased by coating the crystals of our novel composition with a third component, namely a non-hygroscopic, nonacid, long-chain aliphatic compound whidi is solid at room temperature, softens or becomes liquid upon heating, and does not boil below 150' C. Examples of suitable coating agents are mono-, dior tri-alkylamines, havmg at least one long-chain (Cu to Css) radical, for instance octadecylamine, dioctadecylamine, octsdecyl-dllong-chain aliphatic esters or waxes, for instance carnauba wax or montan wax; and paraflin waxes, such as ozocen'te of ceresin, and long-chain alcohols such as cetyl.

This coating can be achieved by stirring the filtered and dried crystals obtained in the mentioned crystallizing step into a melt of the long-chain aliphatic coating agent or into a solution of this agent in an organic solvent. The coating may also be achieved by dry milling the crystals of the primary product in the presence of the coating agent. Finally, the long-chain aliphatic compound may be added to the alcoholic mass in which the primary crystallization takes place, together with or subsequently to the entry of the quaternary nitrogenous base.

The greater color stability thus achieved manifests itself in greater resistance of the composition to color de velopment by contact with acid perspiration from a person's hands or by exposure for long periods of time to humid, COz-laden atmosphere. The coated colorless crystales are also better adapted for use in hectograph carbons, where the required concentration of color in the coating film is very high (being generally from 40 to 60% by weight of the entire film).

The coating with the long-chain aliphatic compound being optional, there is no lower limit to the quantity thereof required. The upper limit is governed by the desire to achieve full coating of the crystals with practical economy and without having so much wax in the product that it will no longer be a freely flowing powder. practice, the quantity of the coating agent will generally be from about to about 50% by weight of the crystalline carbinol composition being treated.

Without limiting our invention, the following examples are given to illustrate our preferred mode of operation. Parts, proportions or percentages, where mentioned, are by weight.

Example 1 To a stirred mixture of 50 g. of crude crystal violet carbinol in 3700 cc. of isopropyl alcohol at room temperature, 10 cc. of a commercial aqueous solution (36%) of benzyl trimethyl ammonium hydroxide were added. The mixture was stirred and heated during 45 min. to reflux temperature (82 C.), and held under reflux until completely discolored (about 1 hr.). The resulting pale yellow solution, after filtering at about 75 C. and cooling, gave the product in the form of long, white, orthorhombic prisms which melted at 194 C.l96 C. These crystals analyzed 11.4% N; (theoretical is 10.8%). They were characterized by unusual stability to color change, a sample having remained colorless for over 4 months when kept in a glass jar which was opened frequently.

A product of the same quality was obtained when the hot filtration was omitted. Likewise, the use of cc. and cc. of the quaternary ammonium base gave the same results.

Example 2 Example 1 was repeated using crystal violet itself (C. I. 681) instead of the carbinol. The procedure was as follows.

To a stirred mixture of 50 g. of crystal violet chloride in 3700 cc. of isopropyl alcohol was added 16.4 g. of aqueous sodium hydroxide. The mixture was stirred and heated to reflux temperature (82 C.), 10 cc. of 36% benzyl trimethyl ammonium hydroxide were added, and the mass was refluxed further until completely discolored (about 1 hour). The resulting pale yellow slurry was filtered at 75 C. to remove the insoluble sodium chloride, and then cooled to give a crystalline product melting at 194 C.-196 C. The product was found to be identical with and of the same quality as the product of Example 1.

Examples 3 to 6 The procedure of Example 1 was repeated, except that in lieu of isopropyl alcohol the following were used in separate experiments:

Example 3: Sec-butyl alcohol, 3500 cc. Example 4: Tert-butyl alcohol, 4000 cc. Example 5: Tert-amyl alcohol, 3400 cc. Example 6: Sec-amyl alcohol, 3100 cc.

Crystals having the same properties as those of Example 1 were obtained in each case.

Example 7 To a stirred mixture of 111 g. of crystal violet carbinol in 1640 g. (2090 cc.) of isopropyl alcohol and 483 g. (541 cc.) of benzene, 8.3 g. of 36% benzyl trimethyl ammonium hydroxide were added. The mixture was stirred and heated to reflux temperature (75% C.), and refluxed until the blue-color of the solution was completely discharged and the mass assumed a pale yellow color. The solution was then cooled to 15-20 C., and the crystalline material was filtered off, washed with 100 g. of isopropanol, and dried in a vacuum oven at 50 C.

Examples 8 to 12 The procedure of Example 1 was repeated except that in lieu of the quaternary base therein named, the following were employed in separate experiments:

Example 8: Choline (trimethyl-hydroxy-ethyl ammonium hydroxide), 8 grams of 50% aqueous solution.

I Example 9: Tetramethyl ammonium hydroxide, 36 grams of 10% aqueous solution.

Example 10: Tetraethyl ammonium hydroxide, 36 grams of 10% aqueous solution.

Example 11: The reaction product of epichlorohydrin with ammonia, prepared according to U. S. P. 1,977,251; 12.5 grams of 32% solution in alcohol.

Example 12: Phenyl-dimethyl-benzyl ammonium hydroxide, 11 grams of 32% aqueous solution.

Example 13 50 grams of ethyl violet (C. I. 682) were treated by the procedure of Example 2. Pale grayish crystals were obtained which were found stable against color development on exposure to air. 1

Other color carbinols treated by us according to the above examples were:

Example 14 N-hexa(n-butyl)-tri(p-aminophenyl)-carbinol, obtained by condensing 2 moles of N-di-n-butyl-aniline with 1 mole of p-(di-n-butyl-amino)-benzaldehyde, followed by oxidation with chloranil.

Example 15 N tetra(n butyl) N diethyl tri(p aminophenyl)- carbinol, obtained as in Example 14 except using p-diethylamino-benzaldehyde.

The products in Examples 14' and 15 are of a semisolid, resinous nature. Their isolation therefore was modified to the extent that filtration was replaced by settling and decantation.

It will be clear that the details of the above examples may be varied widely within theskill of those engaged in this art.

The crude, colored crystal violet carbinol used as starting material in Example 1 is available commercially. It is always highly colored (blue-violet), because it has not been known heretofore how to produce it and keep it under practical storage conditions in a colorless form. The N-ethyl and N-propyl homologs are also operable. Likewise, mixed alkyl derivatives may be used; that is, a given N atom may bear the same or different alkyl groups.

Even when they are the same in a particular N atom, any or all of the alkyl groups on the N atoms in the other rings may be different. Not all of these variants are available commercially. For this reason, crystal violet, ethyl violet, and their bases (i. e. carbinols) are the preferred starting materials.

The alcohols mentioned are usually anhydrous. It is not necessary, however, to be strict in this respect, inasmuch as the desired effect can be achieved also with a solvent having some water in it, say up to 10%. It will be noted in this connection that the quaternary ammonium bases and the NaOH of Example 2 were added in the form of aqueous solutions.

The products of this invention are color-stable carbinol compositions of triarylmethane colors. By stable we mean that the color of the crystals does not revert to the characteristic violet on exposure to air.

The crystals exist in the form of long orthorhombic prisms. They melt with decomposition at about 193 C. 195' C. and contain l1.0-l1.7% N. The theoretical nitrogen content for the pure crystal violet carbinol is 10.8%. The abovementioned values correspond to a composition consisting of the crystal violet carbinol plus about 5% by weight of the quaternary ammonium base.

When these crystals are recrystallized from benzene or its mixtures with ligroin, they become undistinguishable from commercial crystal violet carbinol. In other words, their N analysis drops to the theoretical, and the crystals rapidly develop color upon exposure. This indicates that part of the ammonium base apparently becomes occluded in the crystals of the carbinol and that the thus protected crystals are more stable against conversion into color than is the pure carbinol.

The following additional examples illustrate that modification of our invention wherein the novel colorless compositions of the previous examples are coated with a longchain waxy compound for the sake of imparting thereto extra stability against discoloration by storage in an atmosphere rich with acid fumes such as CO: or $02.

Example 16 A mixture of 5.4 g. of stearyl amine (a commercial mixture of hexadecyl and octadecyl amines) and 350 cc. of isopropanol was heated on a steam bath until a clear solution was obtained. To the heated solution was added 8 g. of the product of Example l and l g. of an aqueous, 36% solution of benzyl trimethyl ammonium hydroxide. The mixture was heated to boiling and filtered hot; on cooling. a crystalline light buff-colored m aterial separated which was then filtered off, washed with 10 g. of isopropanol, and dried.

By spectrographic analysis, the product was found to consist of 85% color (calcd. as crystal violet) and stearylamine. This product showed no discoloration when it was stored without any special precautions for a period of 10 months, during which time the product was frequently exposed to open air in the vicinity of a large chemical plant.

- Example I 7 A mixture of 71 g. of finely powdered stearylamine and 284 g. of the colorless crystal violet carbinol composition of Example 1 was milled in a rotary jar for 6 hours at room temperature. A very uniform product was obtained in the form of a white, nondusting powder. The product possessed unusual stability against discoloration on prolonged exposure to open air.

The treatment with protective coating agent may also be effected in one step with the principal decolorizing treatment. This is illustrated in the following example:

Example 18 The procedure of Example 7 was repeated except that the initial mixture of crystal violet carbinol, isopropyl alcohol, benzene and benzyl-trimethyl-ammonium hydroxide contained further 25 g. of stearylamine. The

mixture was stirred, heated to reflux, and then worked up as in Example 7. The resulting white crystals were coated with stearylamine and were found to be much more stable to storage than those of Example 7.

The desired added stability against storage in an acid laden atmosphere may also be achieved by coating the crystals of our novel colorless carbinol composition with a long-chain fatty ester compound or hydrocarbon cornposiuon such as carnauba wax, montan wax, lanolin, paraffin wax, Vaseline, or mixtures of these. In such cases, however, it must be remembered that the waxes and fatty esters usually possess some residual acidity. This must be neutralized prior to use, preferably by treat ing the fatty compound itself with a quaternary am monium base of the type hereinabove discussed. The following additional examples will illustrate the preferred procedure in such cases.

Example 19 A molten coating composition was prepared by heatmg together on a steam bath 63.6 g. of commercial ctlsirliicauba wax, 112.8 g. of Vaseline, and 23.6 g. of Ian- 0 A 23.4 g. portion of this wax composition was neutralized by adding 0.6 g. of a 36% aqueous solution of benzyl trimethyl ammonium hydroxide and stirring for 15 min. on a steam bath. This was then diluted with 400 cc. of isooctane and stirred at 82-85 C. until a nearly clear solution was obtained.

To this hot solution was added with stirring in small portions over 15 min., g. of the product of Example 1. The mixture was stirred at 82-85 C. for 20 min. then cooled slowly to 28' C. and filtered. The crystals were washed with 50 cc. of isooctane and dried under vacuum to constant weight.

The product was 92 g. of pale yellow, non-dusting crystals, which contained 76% of active ingredient. The crystals melted at 180-190 C. They remained pale yellow on exposure for over 48 hours to open air in an industrial area where acid fumes such as llCl, S01. S01, HBr, Cla, Br: and oxides of nitrogen are present in varying amounts. In contrast, crystal violet carbinol itself is so unstable in this atmosphere that it cannot even be filtered without changing to a fairly deep violet.

A product of similar stability properties was also produced by repeating the procedure of the above example, but omitting the Vaseline and lanoline.

Example 20 When the composition prepared in Example 13 is treated by the procedure of Example 19 above, the product is obtained in the form of white to slightly yellow crystals, melting at about -128 C. The product is extremely stable to handling and storage in the open air.

In lieu of the quaternary ammonium hydroxide designated in Examples 19 to 20 above, other nitrogenous bases, whether quaternary ammonium hydroxides or primary, secondary or tertiary amines, may be used to neu tralize the residual acidity in the wax. Suitable examamples of such other nitrogenous bases are tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, choline, ethanolamine, triethanolamine, and the products of U. S. 1,977,251.

in lieu of isooctane, any other suitable hydrocarbon liquid, for instance gasoline, may be employed to dilute the melt prior to filtration.

The novel carbinol compositions of our invention are readily convertible into color by treatment with solutions of strong acid, by reactive contact with ionizable organic halogen compounds, or by forceful contact with acid reacting clays. Of course, inasmuch as the prin crpal aim of our invention is to avoid smudging the hands of typists and other personnel handling the papers involved in duplicating processes, such development of color is best postponed to a stage simultaneous with or subsequent to the formation of the final copies. The technique of development is therefore varied depending on the process employed for transferring the image. For instance, in spirit'hectograph printing, where transfer is achieved by contacting a moistened copy sheet with the coated face of the master sheet, development is achieved simply by adding an acid or an acid developing halogen compound to the moistening liquid. The latter is usually an alcoholic composition, but it may be someiother polar, volatile solvent, for instance dioxane, diethyl carbonate, dimethyl carbonate, or a Carbitol type solvent (i. e. a lower monoalkyl ether of diethylene glycol).

In impact printing, an acid reacting clay is coated onto the copy sheet, or impregnated into its fibers, or it may be provided as a coating on the transfer sheet itself, being insulated from another coating on the same sheet, containing the colorless carbinol composition, by a film of wax or other suitable, fragile composition. In the case of ordinary typing with carbon copies, the natural acid-clay content of the copy paper may be depended on, or again the paper may be pretreated with a solution of a halogen compound of acid reaction and dried to form a film of the acid substance on its surface.

In all the above cases of dry development, that is.

color development by contact between dry or waxy materials in the absence of water or alcohol, the process may be accelerated by exposing the copy sheet, after receiving the image, to radiant heat for instance from an infra-red lamp.

The following additional examples will illustrate this phase of our invention.

Example 21 0.2 g. of the coated colorless carbinol obtained in Example 16 above was added to a melt of g. carnauba Wax and 1.5 g. lanoline, which had been neutralized with benzyltrimethyl-ammonium hydroxide as in Example 19. After some heating to insure uniform distribution of the coloring agent, the melt was applied in a thin film to chemically neutral, white paper to produce an essentially colorless transfer sheet. When the latter was cool and hard, an uncoated sheet of paper was placed against its coated surface, and by writing with a stylus or by typing on the uncoated paper, a negative image of the letters was transferred to the back of the uncoated paper. This sheet was then used as a master sheet in a rotary duplicating machine for making numerous copies.

Each copy was made by first wetting the surface of a fresh sheet of paper with a 0.5% solution of triphenylchloromethane in methanol, and then pressing it momentarily against the master sheet. A strong and clear positive violet-colored reproduction of the original written or typed message was obtained on every copy.

Example 22 The procedure was essentially as in Example 21, except that no organic chlorine compound was added to the methanol employed for moistening the copy sheets. Iustead,'the natural acidic clay content of the paper, introduced in its manufacture, was depended upon for color development. Development of the image in this case was more slow than in Example 21, but resulted eventually in clear, strongly colored prints, nevertheless.

Example 23 The colorless, wax-coated composition obtained in Ex ample 19 was mixed gently with an equal weight of Attaclay" (a commercial grade of acidic aluminum silicate). This colorless intimate mixture was spread on a hard surface. Local pressure applied to the film produced immediately a strong bluish-violet color over the area of impact.

Example 24 A colorless intimate mixture of equal parts by weight of the product of Example 19 and of triphenylchloromethane was spread in a thin layer on a sheet of paper, which then was placed over a metal screen. This was held for a fraction of a second over a source of radiant heat giving a surface temperature of approximately 80 C. A clear, strong pattern was produced, in which the areas protected by the wires remained white and the remainder was a strong violet color.

Example 25 The colorless intimate mixture prepared in the Example 24 was spread out in a thin layer on several sheets of paper, and these were moistened variously with drops of methanol, ethanol, acetone, and dioxane. Strong violetcolored spots were developed instantly in the moistened areas.

As concerns the chemical nature of the acid-developing agents hereinabove referred to, the same may be mineral or organic acids, for instance sulfuric, phosphoric, hydrochloric, hydrobromic, acetic, stearic, tannic or oxalic.

Or they may be acid-reacting clays such as are commonly used as fillers for paper, for instance Attaplugus clay, magnesium trisilicate, natural zeolites, synthetic zeolite materials of the sodium aluminum silicate type, and mixtures of any of these. Or they may beinorganic or organic halogen compounds which tend to ionize into a strongly acidic halogen atom and a weakly basic cation when contacted with water or an alcohol. such active organic halogen compounds are chloranil, ethylene chlorohydrin, epichlorohydrin, triphenylchloromethane, benzyl chloride, benzal chloride, benzotrichloride, benzophenone dichloride (either unsubstituted or substituted in phenyl rings), benzoyl chloride, acetylchloride, lauroyl chloride, aniline hydrochloride, benzenesulfonyl chloride, p-toluene-sulfonyl chloride, aliphatic sulfonyl chlorides (e. g. those obtained by treating with S02 and Cl: pafaffin hydrocarbons of 12 to 16 C-atoms), cyclohexyl-sulfonyl chloride, p-nitrophenyl-sulfonyl chloride, the chloramines (organic compounds having chlorine attached to nitrogen; Benthsen-Sudborough, Org. Chem., p. 892), aniline hydrochloride, pyridine hydrochloride; and the corresponding bromine compounds of all the above. Examples of suitable inorganic compounds are iodine monochloride (ICl), iodine monobromide, iodine trichloride (ICls) and stearatochromic chloride (CrsHaeCraOaCla) In the case of the mineral acids and the more reactive halogen compounds, e. g. the organic sulfonyl chlorides, high concentrations of the acid substance in the moistening liquid should be avoided, as otherwise there is danger of forming the di-hydrochlorides and tri-hydrochlorides of the triarylmethane color. Inasmuch as the shades of the higher salts of crystal violet, for instance, are different from that of the monohydrochloride and also tinctorially much weaker, such higher salt formation is objectionable. However, keeping the concentration of mineral acid at, say, below 0.1% concentration, will safely avoid the mentioned difiiculty in all cases. With many of the less acidic halogen organic compounds, on the other hand, the danger of going beyond the monohydrochloride is totally absent, and the concentration need not be carefully controlled. Instances of such convenient, self-buffering, halogen compounds are triphenyl chlormethane, chloranil, 2,5- and 2,6-dichloro-p-benzoquinone, N-2,6,-trichlorobenzoquinone-imine, aniline hydrochloride, ethylene chlorhydrin, and various solvent-soluble organo-metal halides, for example stearatochromic chloride, which is available as a solution in isopropanol. The acid-reacting clays are also self-buffering in the above respect.

We claim as our invention:

1. A coloring composition comprising an N-polyalkyltri(p-aminophenyl) carbinol in the form of colorless crystals intimately associated with a quantity of a quaternary ammonium hydroxide corresponding to not less than 2.5% by weight of said carbinol, said coloring composition being Suitable examples of characterized by a retarded tendency to become discolored upon exposure to the atmosphere, and by yielding rapidly the corresponding polyalkyl-triamino triphenyl-methane dye upon contact with acid, the term polyalkyl" in this claim being limited to the presence of not less than and not more than 6 alkyl radicals per molecule and each of said alkyl radicals containing not more than 4 C-atoms.

2. A composition of matter adapted for use as coloring agent for transfer media in duplicating processes, comprising substantially colorless crystals of an N-polyalkyl-tri(paminophenyl) carbinol having occluded within them a quaternary nitrogenous base, said polyalkyl-tri(aminophenyl) carbinol having from 5 to 6 alkyl radicals of not more than 4 C-atoms each attached to its N-atoms; said quaternary nitrogenous base being an ammonium hydroxide whose nitrogen valencies are satisfied by substituents of the group consisting of alkyl, aralkyl, aryl, cycloalkyl, hydroxyalkyl and epihydrin, but which is devoid of sulfo and carboxy groups and is soluble in secondary and tertiary aliphatic, monohydric, saturated alcohols of 3 to 6 carbon atoms, and the quantity of quaternary base being not less than 2.5% by weight of the carbinol.

3. A composition of matter as in claim 2 the quantity of quaternary base being about 5 to by weight of the carbinol.

4. A composition of matter as in claim 2, the carbinol compound being a member of the group consisting of the carbinols of methyl violet, ethyl violet and crystal violet.

5. A composition of matter as in claim 4, the quaternary base being benzyl-trimethyl-ammonium hydroxide.

6. A composition of matter as in claim 4, the quaternary base being tetramethyl-ammonium hydroxide.

7. A composition of matter as in claim 4, the quaternary base being phenyl-dimethyl-benzyl-ammonium hydroxide.

8. A compositoin of matter as in claim 4, the quaternary base being the hydroxide of the quaternary reaction product of epichlorhydrin and ammonia.

9. A coloring composition comprising an N-polyalkyltri(p-aminophenyl) carbinol in the form of colorless crystals intimately associated with a quantity of a quaternary ammonium hydroxide corresponding to not less than 2.5% by weight of said carbinol and with a non-hygroscopic. non-acidic, long-chain aliphatic compound, said coloring composition being characterized by stability against discoloration in storage and upon exposure to humid atmosphere, and by yielding rapidly the corresponding polyalkyl-triamino triphenyl-methane dye upon contact with acid, the term "polyalkyl" in this claim being limited to the presence of not less than 5 and not more than 6 alkyl radicals in the amino groups of each molecule, and each of said alkyl radicals containing not more than 4 C-atoms.

10. A composition of matter adapted for use as coloring agent for transfer media in duplicating processes, comprising substantially colorless crystals of an N-polyalkyl-tri(p-aminophenyl) carbinol having occluded within them a quaternary nitrogenous base in quantity not less than 2.5% by weight and being coated with a non-hygroscopic, non-acidic, long-chain aliphatic compound, said N-polyalkyl-tri(p-aminophenyl) carbinol having from 5 to 6 alkyl radicals of not more than 4 C-atoms each attached to its N-atoms: said quaternary nitrogenous base being an ammonium hydroxide whose nitrogen valencies are satisfied by substituents of the group consisting of alkyl, aralkyl, aryl. cycloalkyl, hydroxyalkyl and epihydrin, but which is devoid of sulfo and carboxy groups and is soluble in secondary and tertiary aliphatic, monohydric, saturated alcohols of 3 to 6 carbon atoms, and said long chain aliphatic compound being a member of the group consisting of long-chain fatty amines. long-chain fatty esters, natural waxes, and parafiin hydrocarbons.

l l. A composition of matter as in claim 10, the quaternary base being present in quantity of about 5 to 10% by weight of the carbinol.

12. A composition of matter as in claim 10, the long- 12 chain aliphatic compound being an alkyl amine of 12 to 20 C-atoms.

13. A composition of matter as in claim 10, the longchain aliphatic compound being a natural wax whose acidity has been neutralized by means of a nitrogenous organic base.

14. A composition of matter as in claim 10, the longchain aliphatic compound being a wax-ester-hydrocarbon mixture adapted for use as a molten vehicle for the color in the process of coating transfer sheets for duplication processes.

15. A process of producing a colorless composition adapted for use as coloring agent in transfer coating for duplication processes, which comprises subjecting to crystallization a triarylmethyl coloring agent of the group consisting of N-polyalltyl-tri(p-aminophenyl) methane colors and the carbinols corresponding to said methane colors, the term "polyalkyl" here implying the presence of not less than 5 and not more than 6 alkyl radicals per molecule, each alkyl radicals containing not more than 4 Catoms, the crystallization being etfected in a non-primary aliphatic alcohol and in the presence of a quaternary nitrogenous base, the quantity of said base being suflicient to convert into carbinol state any salt of said color present in the initial material and to leave a residual quantity of the base, equal in weight to not less than 2.5% by weight of the carbinol, in the crystallized carbinol, and separating the crystallized mass from the alcoholic mother liquor.

16. A process as in claim 15, in which the crystallizing alcohol is a member of the group consisting of secondary and tertiary aliphatic, monohydric, saturated alcohols of 3 to 6 carbon atoms.

17. A process as in claim 15, in which the quaternary nitrogenous base is an ammonium hydroxide whose nitrogen valencies are satisfied by substituents of the group consisting of alkyl, aralkyl, aryl. cycloalkyl, hydroxyalltyl and epihydrin, but which is devoid of sulfo and carboxy groups and is soluble in secondary and tertiary aliphatic, monohydric, saturated alcohols of 3 to 6 carbon atoms.

18. A process as in claim 15, wherein crystallization is effected by heating the crystallization mass until the characteristic triarylmethane color present in the initial material has disappeared, and then cooling to precipitate the decolorized crystals of the coloring agent.

19. A process as in claim 15, wherein the crystallized coloring agent is further treated with a non-hygroscopic, non-acidic, long-chain aliphatic compound, whereby to coat the crystals with said agent and to increase their stability against color development in storage.

20. A process as in claim 19. wherein the coating agent is a member of the group consisting of long-chain alkyl amines, long-chain aliphatic esters, natural waxes, and long-chain paratfin hydrocarbons.

21. A process as in claim 19, wherein the coating agent is added directly to the alcoholic mass in which crystallization takes place.

22. A process as in claim 19, wherein treatment with the coating agent is efiected by treating the isolated colorless crystals of the coloring agent with a dispersion of the coating agent in an organic solvent.

23. A process as in claim 19, wherein treatment with the coating agent is effected by dry milling the isolated colorless crystals of the coloring agent with the coating agent.

24. A process of producing a non-staining transfer medium adapted for use in duplication processes. which comprises coating a transfer sheet with a waxy film containing a colorless coloring composition as defined in claim 2.

25. A process of producing a non-staining transfer medium adapted for use in duplication processes, which comprises coating a transfer sheet with a waxy film containing a colorless coloring composition as defined in claim 10.

26. A transfer sheet adapted for use in duplication processes, said sheet being coated with a waxy film containing an essentially colorless coloring composition which is adapted to yield locally the corresponding polyalkyltriamino triphenyl methane color upon being brought in intimate contact with an acid-reacting substance, said coloring composition comprising substantially colorless crystals of an N-polyalkyl-tri(p-aminophenyl) carbinol as defined in claim 2, in intimate association with a quaternary nitrogenous base as defined in claim 2.

27. The process of developing color in a colorless image produced from a stabilized, colorless coloring composition as defined in claim 10, which comprises bringing the image into intimate contact with an acid reacting substance selected from the group consisting of alcohol-soluble inorganic and organic acids, acid-reacting clays, and alcohol 15 2,634,677

14 soluble organic halogen compounds having a labile halogen atom.

28. The process of developing color from a stabilized colorless coloring composition as defined in claim 10, which comprises bringing said composition into intimate contact with an organic halogen compound which is characterized by solubility in alcohol and by undergoing in its alcoholic solutions partial ionization into a strongly acidic halogen ion and a weakly basic cation.

References Cited in the file of this patent UNITED STATES PATENTS Krzikalla et al Dec. 3, 1940 Adams June 21, 1949 Klimkowski Apr. 14, 1953 

1. A COLORING COMPOSITION COMPRISING AN N-POLYALKYLTRI(P-AMINOPHENYL) CARBINOL IN THE FORM OF COLORLESS CRYSTALS INTIMATELY ASSOCIATED WITH A QUANTITY OF A QUATERNARY AMMONIUM HYDROXIDE CORRESPONDING TO NOT LESS THAN 2.5% BY WEIGHT OF SAID CARBINOL, SAID COLORING COMPOSITION BEING CHARACTERIZED BY A RETARDED TENDENCY TO BECOME DISCOLORED UPON EXPOSURE TO THE ATMOSPHERE, AND BY YIELDING RAPIDLY THE CORRESPONDING POLYALKYL-TRIAMINO TRIPHENYL-METHANE DYE UPON CONTACT WITH ACID, THE TERM "POLYALKYL" IN THIS CLAIM BEING LIMITED TO THE PRESENCE OF NOT LESS THAN 5 AND NOT MORE THAN 6 ALKYL RADICALS PER MOLECULE AND EACH OF SAID ALKYL RADICALS CONTAINING NOT MORE THAN 4 C-ATOMS. 